CN1697336A - Path searcher and path searching method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a path searcher which eliminates sidelobe component of a path which is generated by letting a received signal pass in a band filter from power delay profile, and detects the pass accurately.

Description

Path-searcher and method for searching path

Technical field

Present invention relates in general to a kind of wireless communication technology, more particularly, relate to a kind of path-searcher and method for searching path based on power delay profile (delay profile).

Background technology

Usually, the signal that sends from radio transmitters arrives wireless receiver as ground wave (direct wave).Except that ground wave, perhaps replace ground wave, also arrive wireless receiver from one or more reflected wave of building, barrier or ground return.Ground wave and/or reflected wave constitute a series of arrival ripples on the time shaft, thereby these a series of arrival ripples have formed the multipath power delay profile.In radio communication, amplitude and timing by distinguishing these paths exactly can return to gratifying degree from the primary signal that radio transmitters sends.

The technology that utilization is called " route searching " is come the path of detection power in postponing to distribute regularly.In the route searching of routine, be set to certain level based on the threshold value of noise level, and whether surpass this threshold value according to the power level in path and detect the path based on noise level.The example of conventional path search techniques is disclosed in JP2001-217747A.

Yet regularly different with real path, some path candidate that occurs in the power delay profile is derived from the secondary lobe component in path.For example, when roll-off filter (roll-off filter) is passed through in the relatively large path of power, produce the secondary lobe component in this path, and this secondary lobe component may appear in the power delay profile.In conventional purposes or product, can ignore this secondary lobe component; Yet when being applied to premium quality product in the future, the secondary lobe component may reduce the accuracy of route searching.Be difficult to eliminate this unwanted secondary lobe component based on the threshold value of noise level by regulating, this be because, if will be provided with too lowly based on the threshold value of noise level, then many secondary lobe components can be picked up and be the true path component, and if De Taigao will be set based on the threshold value of noise level, then not only can eliminate unwanted secondary lobe component but also can eliminate the true path component.In this case, the suitable secondary lobe component of power level that in power delay profile, has power level and true path component.

Simultaneously, in the multiple-input and multiple-output that is designed to realize high message capacity (MIMO) system, in transmitter/receiver, use a plurality of transmitting antennas and a plurality of reception antenna.Therefore, as depicted in figs. 1 and 2, multipath not only from a transmitting antenna 206-p to the propagation path of certain reception antenna 208-x, occurs and disturb, and the multipath interference from another transmitting antenna 206-q to the path of described reception antenna 208-x, also occurs.In mimo system, along with antenna amount increases, path candidate also increases, and needs the route searching of high accuracy.Simultaneously, the deterioration of route searching accuracy is the problem that attracts people's attention.

Summary of the invention

Imagined the present invention in view of the above problems, the purpose of this invention is to provide a kind of path-searcher and method for searching path, its the secondary lobe component that can remove the path from power delay profile to be correctly detecting true path, and these secondary lobe components are that the signal that receives produces during by the frequency band limits filter.

In order to realize this purpose, according to the signal creation power delay profile that receives, and according to the secondary lobe component of the response characteristic calculating path of frequency band limits filter.Remove the secondary lobe component from power delay profile, generating calibrated power delay profile, and detect the path regularly according to calibrated power delay profile.

In one aspect of the invention, a kind of path-searcher comprises:

(a) power delay profile generation unit is constituted as according to the signal that receives and generates power delay profile;

(b) secondary lobe component determining unit is constituted as the response characteristic of utilizing the frequency band limits filter and discerns the secondary lobe component;

(c) power delay profile correcting unit is constituted as and removes described secondary lobe component from described power delay profile, postpones to distribute with corrected power; And

(d) path timing detecting unit is constituted as according to calibrated power delay profile and detects the path regularly.

In another aspect of this invention, provide a kind of method for searching path.This method for searching path may further comprise the steps:

(a) according to the signal creation power delay profile that receives;

(b) select power level to surpass the path of threshold level;

(c) discern the secondary lobe component in selected path according to the response characteristic of frequency band limits filter;

(d) from described power delay profile, remove described secondary lobe component, to generate calibrated power delay profile; And

(e) detect the path regularly according to calibrated power delay profile.

Utilize this path-searcher and method for searching path, the path secondary lobe component that has produced when having removed the signal that receives by the frequency band limits filter efficiently from power delay profile, this secondary lobe component is to remove by the threshold value of regulating simply based on noise level.Therefore, can carry out accurate and reliable path detection.

If above-mentioned path search techniques is applied to mimo system, can create power delay profile at each (every propagation path that limits by transmission path and RX path) in the combination of transmitting antenna and reception antenna so.

In the case, for example can these power delay profile be synthesized single distribution by a plurality of power delay profile are averaged.Can be according to the secondary lobe that comes calculating path through average power delay profile.When according to carrying out the detection of secondary lobe component through average power delay profile and when removing, provide based on regularly, so can reduce the required arithmetical operation amount of input through the path of average power delay profile because handle to input subsequently.If in input, give priority, wish so in the power delay profile of creating at many propagation paths each is proofreaied and correct, rather than these power delay profile are averaged accuracy.

Description of drawings

The following detailed description that reads in conjunction with the accompanying drawings, other purposes of the present invention, feature and advantage are more obvious, in the accompanying drawings:

Fig. 1 is the schematic diagram that power delay profile is shown;

Fig. 2 is the schematic diagram that mimo wireless communication system is shown;

Fig. 3 is the schematic diagram of MIMO receiver;

Fig. 4 is the block diagram according to the path-searcher that is used for the MIMO receiver of the embodiment of the invention;

Fig. 5 is the curve chart that synthetic power delay profile is shown;

Fig. 6 is the curve chart of the pusle response characteristics of roll-off filter;

Fig. 7 is the flow chart that illustrates according to the operation of the path-searcher of the embodiment of the invention;

Fig. 8 is the figure that the simulation result that this embodiment compares with routine techniques is shown; And

Fig. 9 is the block diagram that is used for the path-searcher of MIMO receiver according to another embodiment of the present invention.

Embodiment

Describe the present invention below in conjunction with accompanying drawing.

Fig. 2 is the schematic diagram that comprises multiple-input and multiple-output (MIMO) communication system of transmitter 202 and receiver 204.The mimo system that present embodiment uses is the spatial multiplexing MIMO system, sends each signal simultaneously from transmitting antenna 206-1 to 206-N with same frequency.The present invention can be applied to wherein send simultaneously from transmitting antenna the MIMO diversity system of the essentially identical signal of content.Receive a plurality of signals that send from transmitting antenna 206-1 to 206-N to 208-N at a plurality of reception antenna 208-1.In this example, for simplicity, the quantity of transmitting antenna identical with the quantity of reception antenna (a N antenna).Yet transmitting antenna can be different with the antenna amount between the reception antenna.

Fig. 3 is the schematic diagram of receiver 204 shown in Figure 2.The received signal y that receives at each reception antenna place ₁To y _NBe input to detecting signal unit 302.Received signal y ₁To y _NAlso be input to path-searcher 304.Path-searcher is estimated channel according to the signal that receives (it comprises the known pilot signal of transmitter 202 and receiver 204), creates power delay profile, and provides about the path regularly and the information of fading compensation to detecting signal unit 302.

Detecting signal unit 302 according to the path of signal that receives and estimation regularly to detecting to the signal that 206-N sends respectively from a plurality of transmitting antenna 206-1, and makes it separated from one another.Can use the Maximum Likelihood Detection (QRM-MLD) of Minimum Mean Square Error (MMSE), Maximum Likelihood Detection (MLD) or QR decomposition and M algorithm to carry out Signal Separation.Separated signal offers the channel decoder that is used for decoding processing subsequently.

Fig. 4 is the functional block diagram according to the path-searcher 304 of the embodiment of the invention.Path-searcher 304 comprises regularly detecting unit 408 of power delay profile generation unit 402, power delay profile averaging unit 404, secondary lobe generation unit 406, secondary lobe removal unit 407 and path.

Power delay profile generation unit 402 is according to the received signal y that receives to the 208-N place at reception antenna 208-1 and carried out the frequency band limits processing ₁To y _NGenerate a plurality of power delay profile.More particularly, power delay profile generation unit 402 is carried out channel estimating according to the pilot signal that receives to transmitting antenna 206 and each combination of reception antenna 208, inspection is included in the power level and the timing in the path in the received signal, and output is about the item of information of power delay profile.Therefore, power delay profile generation unit 402 generates N _Tx* N _RxIndividual power delay profile, wherein, N _TxThe quantity of expression transmitting antenna 206, N _RxThe quantity of expression reception antenna 208.In mimo system, the signal that receives at reception antenna 208 places comprises and is derived from N _TxThe signal of individual transmitting antenna 206.Can utilize transmitting antenna 206-1 in the 206-N different pilot signal with the N of transmitting antenna 206 with reception antenna 208 _Tx* N _RxIndividual combination is distinguished mutually.Preferably, so that its orthogonal mode is selected pilot signal.

Power delay profile averaging unit 404 synthesizes single distribution with these a plurality of power delay profile when a plurality of power delay profile that power delay profile generation unit 402 is created are carried out suitably timing.Usually can synthesize power delay profile by averaging (for example arithmetic average or weighted arithmetic mean).For this reason, power delay profile averaging unit 404 is examples of power delay profile synthesizer.

Fig. 5 is the figure that the example of synthetic power delay profile is shown.This power delay profile comprises that power level surpasses 9 paths (being represented by downward arrow) based on the threshold value Eth of noise level.In these 9 paths, 6 paths 501 to 506 are true path, and 3 secondary lobe components (real channel of these components does not exist) that path 511 to 513 may be a true path.Be true path if the secondary lobe component detected mistakenly, just may reduce the accuracy of the Signal Separation of carrying out at detecting signal unit 302 places in the subsequent treatment, and may be difficult to realize that gratifying signal recovers.The secondary lobe component is to produce when roll-offing (frequency band limits) filter when the higher relatively path of power level.

Secondary lobe generation unit 406 shown in Figure 4 utilizes the pusle response characteristics of roll-off filter (frequency band limits filter), generates the secondary lobe component that comes across power delay profile.The pusle response characteristics h of known roll-off filter in receiver 204 _RC(t).Pusle response characteristics h _RC(t) for example have characteristic shown in Figure 6, and represent by formula (1).

$h_{\mathrm{RC}}\left(t\right)=\left(\frac{\sin (\mathrm{\πt}/\mathrm{Tc})}{\mathrm{\πt}/\mathrm{Tc}}\right)\left(\frac{\cos (\mathrm{\π\αt}/\mathrm{Tc})}{1-{(4\mathrm{\αt}/(2\mathrm{Tc}\left)\right)}^2}\right)---\left(1\right)$

Wherein, Tc represents chip period, and α represents roll-off factor.In the example depicted in fig. 6, α is set to 0.22 (α=0.22).Usually, the scope from negative chip period to positive chip period (| the part in the t|≤Tc) is called the main lobe that points to true path, and other are in scope | the part sensing secondary lobe in t|＞Tc.

For example, according to the power level and the timing in the first arrival path 501 shown in Figure 5, can calculate the power level and the timing of the secondary lobe in this path by formula (1).Power level and timing according to the second arrival path 502 can utilize formula (1) to determine the secondary lobe in path 502.Similarly, select the relatively large path (for example, Y path) of power level, and determine the secondary lobe component in each selected path.In theory, there are many secondary lobe components, select the secondary lobe component (for example, the Z on the main lobe either side secondary lobe component) of needs quantity according to purposes.Determine the power level and the timing of selected secondary lobe component at each path.Can surpass the path of selecting it is calculated the secondary lobe component those paths of threshold level by the descending (Y the path that for example, has Y highest power level) of power level from its power level.

Secondary lobe shown in Figure 4 is removed unit 407 and remove the secondary lobe component that secondary lobe generation unit 406 identifies from the power delay profile that power delay profile averaging unit 404 generates.Therefore, having removed 511,512 and 513,6 true path 501 to 506 in undesirable path from power delay profile shown in Figure 5 is retained in the power delay profile.

The path is extracted regularly according to removed the power delay profile of proofreading and correct unit 407 by secondary lobe in path regularly detecting unit 408.In the example depicted in fig. 5, thus extract 6 paths 501 to 506 by the path power level and based on the comparison between the threshold value Eth of noise level.

In this way, therefore the path-searcher 304 of present embodiment, can realize route searching accurately based on coming executive path search from the power delay profile of wherein having removed undesirable path components.

Fig. 7 is the flow chart that the operation of carrying out according to the path-searcher 304 of the embodiment of the invention is shown.This flow process shows the example of selecting Y the highest path from power delay profile.Processing begins in step 71.In step 72, at power delay profile generation unit 402 places shown in Figure 4, according to received signal, at each the generation power delay profile in the combination of transmitting antenna in the mimo system and reception antenna.Then, by arithmetic average, weighted average or other proper methods, a plurality of power delay profile that generate are synthesized single power delay profile.

In step 73, selecting power level in a plurality of paths that comprise from synthetic power delay profile is the high path of N.The initial value of parameter N is made as 1 (N=1).

In step 74, according to the timing and the power level in selected path, utilize the response characteristic of (or frequency band limits) filter that roll-offs as shown in Equation (1), secondary lobe generation unit 406 computational rules quantity (for example, Z) secondary lobe component.

In step 75, secondary lobe is removed unit 407 and remove Z secondary lobe component that identifies from the synthetic power delay profile in selected path (path that N is high), and parameter N adds 1.

In step 76, determine whether N is less than or equal to Y (N≤Y).If N is less than or equal to Y (is "Yes" in step 76), then handles and return step 73, next path that selection has next maximal power level, and repeating step 74-76.If N is greater than Y in step 76, then handles and proceed to step 77.At this moment, power delay profile is proofreaied and correct,, and do not comprise the secondary lobe component of Y maximum path so that it comprises the main lobe component of Y maximum path and than the main lobe component and the secondary lobe component of small path.

In step 77, determine the power level in Y maximum path and other paths and regularly according to calibrated power delay profile, handle and finish in step 78.

Fig. 8 is the figure that the simulation result of comparing with routine techniques according to the route searching of present embodiment is shown.The condition that is provided with in the emulation is as follows:

Modulation system: 8PSK

Turbo encoding rate R:3/4

Maximum doppler frequency f _D: 20Hz

The ratio of pilot power and data channel: 30%

Maximum finger quantity: 6

In emulation, use 2db exponential damping 6 path signal models, power level each place, path decay 2db in second path and successor path.The transverse axis of this figure is represented every bit noise average power density of every reception antenna than (Eb/No), and the longitudinal axis is represented average block error rate (BLER).Black circle is represented the perfect estimation result of ingenious calculating, and they also represent to estimate limit.Be positioned at the estimated result of representing very much present embodiment near white circle, triangle and the square at ideal curve place.Be plotted in square, triangle, fork mark and del in the ellipse and represent the estimated result of conventional method.

The different threshold values (Eth) of four kinds of symbolic representation route searching power levels of the estimated result of conventional method.Square expression power threshold is set to certain reference power level P _A(Eth=P _A) time estimated result, triangle represents that power threshold is set to reference power level P _A3 times of (Eth=3 * P _A) time estimated result, the fork mark represent that this threshold value is set to reference power level P _A5 times of (Eth=5 * P _A) time estimated result, and del represents that this threshold value is set to reference power level P _A7 times of (Eth=7 * P _A) time estimated result.The reference power level that uses in this emulation is then the power level in remaining path to be averaged the average power level of determining by removing 24 maximum paths from power delay profile.When threshold level was provided with too lowly, estimated result can not be satisfactory.This is because the path that is chosen as above this threshold value also comprises undesirable path except that true path.When threshold value was provided with De Taigao, estimated result can not be satisfactory, because fail to select some power level to be lower than the true path of this threshold value.

The varying number (Y) of the secondary lobe component that three symbolic representations of the estimated result of present embodiment are to be removed.The power threshold that is used for route searching is set to the twice (Eth=2 * P of reference power level _A).Estimated result (Y=1) when triangle represents to remove secondary lobe component on the every side that appears at true path.Estimated result (Y=2) when two secondary lobe components on the every side that appears at true path are removed in square expression.Estimated result (Y=3) when circle represents to remove three secondary lobe components on the every side that appears at true path.In either case, all very near ideal curve (being limited by black circle), this estimated result with conventional method is different for estimated result.

Fig. 9 is the functional block diagram of path-searcher according to another embodiment of the present invention.Path-searcher shown in Figure 9 comprise power delay profile generation unit 402, N secondary lobe generation unit 406-n, a N secondary lobe remove unit 407-n and N path timing detecting unit 408-n (n=1 ..., N _All).Therefore, the path-searcher of present embodiment has N _AllPaths scounting line, wherein N _All=N _Tx* N _Rx, N _TxThe quantity of expression transmitting antenna, N _RxThe quantity of expression reception antenna.

Power delay profile generation unit 402 carries out channel estimating according to the pilot signal that receives to each combination of transmitting antenna and reception antenna, and creates N _Tx* N _RxIndividual power delay profile.Can utilize pilot signals different in a plurality of transmitting antennas, with the N of transmitting antenna and reception antenna 208 _Tx* N _RxIndividual combination is distinguished from each other and comes.Each power delay profile all offers corresponding secondary lobe generation unit 406 and secondary lobe is removed unit 407.Because N _AllThe parts that comprise in the paths scounting line have identical structure and identical functions, so only the parts that comprise in the first via path search line are described.

Secondary lobe generation unit 406-1 utilizes the roll-off filter pusle response characteristics of (its characteristic is represented in publicity (1)), generates the secondary lobe component that occurs in the power delay profile.Determine the quantity of the expression power level that will generate and secondary lobe component regularly according to purposes.

Secondary lobe is removed unit 407-1 and remove the secondary lobe component that secondary lobe generation unit 406-1 identifies from the power delay profile that power delay profile generation unit 402 generates.The path is extracted regularly according to the power delay profile of having been undertaken proofreading and correct by secondary lobe removal unit 407-1 in path regularly detecting unit 408.

In the present embodiment, not to N _AllIndividual power delay profile averages, but carries out to the removal of secondary lobe component with to the path timing detection at each power delay profile.Path regularly testing result offers detecting signal unit shown in Figure 3 302.Compare with last embodiment, detecting signal unit 302 based at according to the combination of transmitting antenna and reception antenna and the path accurately that mutually different each propagation path is determined regularly, thereby carry out Signal Separation more accurately.

Present patent application is based on the Japanese patent application No.2004-144180 that submitted on May 13rd, 2004 and require its priority than submission date morning, is incorporated herein by reference in its entirety.

Claims (9)

1, a kind of path-searcher that is used for receiver, it comprises:

The power delay profile generation unit is constituted as the signal that receives according to described receiver and generates power delay profile;

The secondary lobe generation unit is constituted as the response characteristic according to the frequency band limits filter of described receiver, and identification is included in the secondary lobe component in the path in the described power delay profile;

Secondary lobe is removed the unit, is constituted as from described power delay profile and removes described secondary lobe component, to generate calibrated power delay profile; And

The path is detecting unit regularly, is constituted as according to described calibrated power delay profile and detects the path regularly.

2, path-searcher as claimed in claim 1, wherein,

Be imported into described power delay profile generation unit from a plurality of transmission antennas transmit and at a plurality of signals that a plurality of reception antennas of described receiver receive, described power delay profile generation unit generates power delay profile at each combination of one of described a plurality of transmitting antennas and one of described a plurality of reception antennas.

3, path-searcher as claimed in claim 2, it also comprises:

The path profile synthesis unit is constituted as the power delay profile that generates corresponding to described combination is synthesized,

Wherein, described secondary lobe generation unit generates the secondary lobe component in path at synthetic power delay profile.

4, path-searcher as claimed in claim 2, wherein, described secondary lobe generation unit generates the secondary lobe component in path in the power delay profile that generates corresponding to described combination each.

5, a kind of receiver, it comprises:

Antenna is constituted as received signal;

The frequency band limits filter is constituted as the unnecessary frequency component of removal from the described signal that receives;

The power delay profile generation unit is constituted as according to the described signal that receives and generates power delay profile;

The secondary lobe generation unit is constituted as the response characteristic according to described frequency band limits filter, and identification is included in the secondary lobe component in the path in the described power delay profile;

Secondary lobe is removed the unit, is constituted as from described power delay profile and removes described secondary lobe component, to generate calibrated power delay profile; And

The path is detecting unit regularly, is constituted as according to described calibrated power delay profile and detects the path regularly.

6, receiver as claimed in claim 5, wherein:

Described antenna comprises a plurality of reception antennas, and each reception antenna all is constituted as the signal of reception from a plurality of transmitting antennas; And

Described power delay profile generation unit generates at each combination of one of described a plurality of transmitting antennas and one of described a plurality of reception antennas and postpones to distribute.

7, receiver as claimed in claim 6, it also comprises:

The path profile synthesis unit is constituted as the power delay profile that generates corresponding to described combination is synthesized,

Wherein, described secondary lobe generation unit generates the secondary lobe component in path at synthetic power delay profile.

8, receiver as claimed in claim 6, wherein, described secondary lobe generation unit generates the secondary lobe component in path in the power delay profile that generates corresponding to described combination each.

9, a kind of method for searching path, it may further comprise the steps:

Generate power delay profile according to the signal that receives;

From described power delay profile, select to surpass the path of threshold value;

Discern the secondary lobe component in selected path according to the response characteristic of frequency band limits filter;

Remove described secondary lobe component from described power delay profile, to generate calibrated power delay profile; And

Detect the path regularly according to described calibrated power delay profile.

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